#include <ft2build.h>
#include FT_FREETYPE_H
#include "Graphics.h"

#include <bx/math.h>

#include <iostream>
#include <optional>

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

namespace {
	using namespace ADVect::Graphics;

	bgfx::ShaderHandle loadShader(const std::string& FILENAME)
	{
		std::string shaderPath{};

		switch (bgfx::getRendererType()) {
		case bgfx::RendererType::Noop:
		case bgfx::RendererType::Direct3D9:  shaderPath = "shaders/dx9/";   break;
		case bgfx::RendererType::Direct3D11:
		case bgfx::RendererType::Direct3D12: shaderPath = "shaders/dx11/";  break;
		case bgfx::RendererType::Gnm:        shaderPath = "shaders/pssl/";  break;
		case bgfx::RendererType::Metal:      shaderPath = "shaders/metal/"; break;
		case bgfx::RendererType::OpenGL:     shaderPath = "shaders/glsl/";  break;
		case bgfx::RendererType::OpenGLES:   shaderPath = "shaders/essl/";  break;
		case bgfx::RendererType::Vulkan:     shaderPath = "shaders/spirv/"; break;
		}


		std::string filePath = shaderPath + FILENAME;

		FILE* file = fopen(filePath.c_str(), "rb");
		fseek(file, 0, SEEK_END);
		long fileSize = ftell(file);
		fseek(file, 0, SEEK_SET);

		const bgfx::Memory* mem = bgfx::alloc(fileSize + 1);
		fread(mem->data, 1, fileSize, file);
		mem->data[mem->size - 1] = '\0';
		fclose(file);

		return bgfx::createShader(mem);
	}

	struct PosUVVertex {
		f32 x;
		f32 y;
		f32 z;
		f32 u;
		f32 v;
	};

	static PosUVVertex quad_vert[] =
	{
		{ 0.f, 0.f, 0.0f, 0.0f, 0.0f },
		{ 0.f, 1.f, 0.0f, 0.0f, 1.0f },
		{ 1.f, 0.f, 0.0f, 1.0f, 0.0f },
		{ 1.f, 1.f, 0.0f, 1.0f, 1.0f }
	};

	static const uint16_t quad_indices[] =
	{
		0, 2, 1,
		1, 2, 3
	};

	FT_Library library;
	FT_Error error;

	struct Font {
		FT_Face face = nullptr;
		std::unordered_map<NVL::Char, bgfx::TextureHandle> cache{};

		void cache_char(NVL::Char c) {
			FT_GlyphSlot slot = face->glyph;

			error = FT_Load_Char(face, c, FT_LOAD_RENDER);
			if (error) {
				std::cerr << "ADV: Failed to load character" << std::endl;
			}

			if (cache.find(c) == cache.end() && slot->bitmap.width != 0) {
				const bgfx::Memory* buf = bgfx::copy(slot->bitmap.buffer, slot->bitmap.pitch * slot->bitmap.rows);

				cache.emplace(c, bgfx::createTexture2D(
					slot->bitmap.width,
					slot->bitmap.rows,
					false,
					1,
					bgfx::TextureFormat::A8,
					BGFX_TEXTURE_NONE | BGFX_SAMPLER_UVW_CLAMP,
					buf
				));
			}
		}
	};

	std::optional<Font> init_font(const char* path) {
		Font f;

		error = FT_New_Face(library, path, 0, &f.face);
		if (error == FT_Err_Unknown_File_Format) {
			std::cerr << "ADV: FreeType Unknown_File_Format: " << error << std::endl;
			return std::nullopt;
		}
		else if (error) {
			std::cerr << "ADV: FreeType font loading error: " << error << std::endl;
			return std::nullopt;
		}

		error = FT_Set_Char_Size(f.face, 0, 20 * 64, 72, 72);
		if (error) {
			std::cerr << "ADV: FreeType Set_Char_Size error: " << error << std::endl;
			return std::nullopt;
		}

		return f;
	}

	void destroy_font(Font& f) {
		FT_Done_Face(f.face);
		for (auto it = f.cache.begin(); it != f.cache.end(); it++) {
			bgfx::destroy(it->second);
		}
	}

	inline bgfx::ProgramHandle load_shader_program(const std::string& shader) {
		return bgfx::createProgram(loadShader(shader + ".vert.bin"), loadShader(shader + ".frag.bin"), true);
	}

	std::optional<ImageTexture> get_image_texture(const std::string& file) {
		ImageTexture i;
		i.buffer = stbi_load(file.c_str(), &i.w, &i.h, &i.channels, 0);
		if (i.buffer == NULL) {
			std::cerr << "ADV: STB IMAGE loading failed" << std::endl;
			return std::nullopt;
		}
		const bgfx::Memory* buf = bgfx::makeRef(i.buffer, i.w * i.h * i.channels * sizeof(u8));
		i.tx = bgfx::createTexture2D(
			i.w,
			i.h,
			false,
			1,
			i.channels == 4 ? bgfx::TextureFormat::RGBA8 : bgfx::TextureFormat::RGB8,
			BGFX_TEXTURE_NONE | BGFX_SAMPLER_UVW_CLAMP,
			buf
		);
		return i;
	}

	void destroy_image_texture(ImageTexture& i) {
		stbi_image_free(i.buffer);
		bgfx::destroy(i.tx);
	}

	Font regular, bold;
	bgfx::ProgramHandle a_program, img_program;
	bgfx::UniformHandle s_texColor;

	bgfx::IndexBufferHandle ibh;
	bgfx::VertexBufferHandle vbh;
	bgfx::VertexLayout pcvDecl;

	std::unordered_map<std::string, ImageTexture> imgs;
}

namespace ADVect::Graphics {
	bool Init(u16 width, u16 height) {
		error = FT_Init_FreeType(&library);
		if (error) {
			std::cerr << "ADV: FreeType init error: " << error << std::endl;
			return false;
		}

		if (auto f = init_font("SourceHanSerif-Regular.ttc")) regular = *f; else return false;
		if (auto f = init_font("SourceHanSerif-Heavy.ttc")) bold = *f; else return false;

		pcvDecl.begin()
			.add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float)
			.add(bgfx::Attrib::TexCoord0, 2, bgfx::AttribType::Float)
			.end();
		ibh = bgfx::createIndexBuffer(bgfx::makeRef(quad_indices, sizeof(quad_indices)));
		vbh = bgfx::createVertexBuffer(bgfx::makeRef(quad_vert, sizeof(quad_vert)), pcvDecl);

		img_program = load_shader_program("test");
		a_program = load_shader_program("swizzle_aaaa");

		s_texColor = bgfx::createUniform("s_texColor", bgfx::UniformType::Sampler);

		return true;
	}

	void Shutdown() {
		destroy_font(regular);
		destroy_font(bold);
		FT_Done_FreeType(library);

		for (auto it = imgs.begin(); it != imgs.end(); it++) {
			destroy_image_texture(it->second);
		}

		bgfx::destroy(a_program);
		bgfx::destroy(img_program);

		bgfx::destroy(ibh);
		bgfx::destroy(vbh);

		bgfx::destroy(s_texColor);
	}

	// Draws quad with texture on Z = 0
	void DrawTexture(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h, u64 state, const bgfx::ProgramHandle& pg) {
		float mtx1[16], mtx2[16], mtx3[16];
		bx::mtxTranslate(mtx1, pos_x, pos_y, 0.0f);
		bx::mtxScale(mtx2, w, h, 1.0f);
		bx::mtxMul(mtx3, mtx2, mtx1);

		bgfx::setTransform(mtx3);

		bgfx::setVertexBuffer(0, vbh);
		bgfx::setIndexBuffer(ibh);

		bgfx::setTexture(0, s_texColor, tex);

		bgfx::setState(state);
		bgfx::submit(0, pg);
	}

	void DrawTextureImage(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h) {
		DrawTexture(tex, pos_x, pos_y, w, h, (BGFX_STATE_DEFAULT | BGFX_STATE_BLEND_ALPHA) & ~(BGFX_STATE_WRITE_Z | BGFX_STATE_DEPTH_TEST_LESS), img_program);
	}

	void DrawTextureImage(const ImageTexture& img, i32 pos_x, i32 pos_y) {
		DrawTextureImage(img.tx, pos_x, pos_y, img.w, img.h);
	}

	ImageTexture* GetImageTextureFromFile(const std::string& file) {
		if (imgs.find(file) == imgs.end()) {
			ImageTexture img;
			if (auto i = get_image_texture(file)) {
				img = *i;
				imgs[file] = std::move(img);
				return &imgs[file];
			}
		}
		return nullptr;
	}

	void DrawTextureStencilAlpha(const bgfx::TextureHandle& tex, i32 pos_x, i32 pos_y, u32 w, u32 h) {
		DrawTexture(tex, pos_x, pos_y, w, h, (BGFX_STATE_DEFAULT | BGFX_STATE_BLEND_ALPHA) & ~(BGFX_STATE_WRITE_Z | BGFX_STATE_DEPTH_TEST_LESS), a_program);
	}

	void RenderString(const NVL::String& s, u32& pos_x, u32& pos_y, u32 col, u32 style_flags) {
		Font* f = &regular;
		switch (style_flags) {
		case TEXT_NONE: break;
		case TEXT_BOLD: f = &bold;  break;
		case TEXT_ITALIC: break;
		case TEXT_ITALIC | TEXT_BOLD: break;
		}

		FT_GlyphSlot& slot = f->face->glyph;
		for (const auto& c : s) {
			f->cache_char(c);

			pos_x += slot->bitmap_left;
			float ypos = pos_y - (slot->bitmap.rows - slot->bitmap_top);

			if (slot->bitmap.width != 0) {
				DrawTextureStencilAlpha((f->cache)[c], pos_x, ypos, slot->bitmap.width, slot->bitmap.rows);
			}

			pos_x += slot->advance.x >> 6;
			pos_y += slot->advance.y >> 6;
		}
	}

	void RenderString(const NVL::String& s, u32&& pos_x, u32&& pos_y, u32 col, u32 style_flags) {
		u32 x = pos_x, y = pos_y;
		RenderString(s, x, y, col, style_flags);
	}

	void RenderStringMarkup(const std::vector<NVL::Environment::Variable>& s, u32 pos_x, u32 pos_y, u32 col) {
		const NVL::String& str = std::get<NVL::String>(s[0].value);

		std::vector<NVL::Environment::Markup> ms{};
		for (const NVL::Environment::Variable& markup : std::get<std::vector<NVL::Environment::Variable>>(s[1].value)) {
			ms.push_back(NVL::Environment::UnpackMarkupVariable(markup));
		}
		
		if (ms.empty()) {
			RenderString(str, pos_x, pos_y, col, TEXT_NONE);
			return;
		}

		if (ms[0].begin != 0)
			RenderString(str.substr(0, ms[0].begin), pos_x, pos_y, col, TEXT_NONE);

		// We assume markups are already sorted
		for (size_t i = 0; i < ms.size(); i++) {
			u32 style_flags = TEXT_NONE;
			const NVL::String* ruby = nullptr;

			for (const auto& e : ms[i].efs) {
				if		(e.first == u"b")	{ style_flags |= TEXT_BOLD; }
				else if (e.first == u"i")	{ style_flags |= TEXT_ITALIC; }
				else if (e.first == u"u")	{ style_flags |= TEXT_UNDERLINE; }
				else if (e.first == u"s")	{ style_flags |= TEXT_STRIKETHROUGH; }
				else if (e.first == u"o")	{ style_flags |= TEXT_OVERLINE; }
				else if (e.first == u"rb")	{ ruby = &e.second[0]; }
				else {
					std::cerr << "ADV: Unrecognized text markup: " << NVL::to_std_string(e.first) << std::endl;
				}
			}

			if (ruby != nullptr) {
				u32 temp_x = pos_x, temp_y = pos_y + 20;
				RenderString(*ruby, temp_x, temp_y, col, TEXT_NONE);
			}

			RenderString(str.substr(ms[i].begin, ms[i].end - ms[i].begin), pos_x, pos_y, col, style_flags);

			if (i != ms.size() - 1 && ms[i + 1].begin - 1 != ms[i].end)
				RenderString(str.substr(ms[i].end, ms[i + 1].begin - ms[i].end), pos_x, pos_y, col, TEXT_NONE);

		}

		if (ms.back().end != str.length())
			RenderString(str.substr(ms.back().end), pos_x, pos_y, col, TEXT_NONE);
	}
}